title: Hexadecylamine adsorption at the iron oxide-oil interface.
abstract: The adsorption behavior of a model additive, hexadecylamine, onto an iron surface from hexadecane oil has been characterized using polarized neutron reflectometry, sum-frequency generation spectroscopy, solution depletion isotherm, and X-ray photoelectron spectroscopy (XPS). The amine showed a strong affinity for the metal surface, forming a dense monolayer at relatively low concentrations; a layer thickness of 16 (±3) Å at low concentrations, increasing to 20 (±3) Å at greater amine concentrations, was determined from the neutron data. These thicknesses suggest that the molecules in the layer are tilted. Adsorption was also indicated by sum-frequency generation spectroscopy and XPS, the latter indicating that the most dominant amine-surface interaction was via electron donation from the nitrogen lone pair to the positively charged iron ions. Sum-frequency generation spectroscopy was used to determine the alkyl chain conformation order and orientation on the surface.
authors.affiliation: Department of Chemistry and BP Institute, Cambridge University , Cambridge CB2 1EW, United Kingdom.
authors.forename: Mary H
authors.initials: MH
authors.lastname: Wood
authors.forename: Rebecca J L
authors.initials: RJ
authors.lastname: Welbourn
authors.forename: Timothy
authors.initials: T
authors.lastname: Charlton
authors.forename: Ali
authors.initials: A
authors.lastname: Zarbakhsh
authors.forename: M T
authors.initials: MT
authors.lastname: Casford
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Clarke